HOW TO: Fail-Safe Gates

Despite having a threshold control, the average noise gate often doesn’t know when to stay closed. As a sustained electric guitar chord fades out and the signal fluctuates slightly in volume around the threshold level, most gates will chatter, opening and closing rapidly and repeatedly. Constant amp hiss is distracting enough, but hiss that stutters like a typewriter is far worse!

Gating out mic bleed on tom tom tracks offers a similar challenge: As the volume of a struck tom decays to just below threshold level, minor fluctuations in mic bleed can push the signal temporarily back over the top. Chatterbox city!

Fortunately, the very best gates offer a solution—either a hysteresis control or two thresholds—that all but guarantee perfect gating action. Two recently introduced plug-ins deliver the goods. Not just superior gates, they each provide other powerful processing, too.

BRAINWORX BX_CONSOLE

Brainworx’s bx_console (reviewed in Electronic Musician’s April 2016 issue) models a rare 72-channel Neve VXS analog mixer. Each iteration of the plug-in emulates one (mono configuration) or two (stereo) channel strips. Each channel strip includes highpass and lowpass filters, 4-band EQ, a limiter/compressor, and the focus of this article: an advanced gate/expander.

Fig. 1. The Brainworx bx_console’s gate features a Hysteresis control (on the left side of the GUI, it’s the fourth knob from the bottom) that makes it open at a different threshold from where it closes. bx_console’s gate offers both Threshold and Hysteresis controls (see Figure 1). The Threshold control sets the level at which the gate will close. The Hysteresis control sets a separate threshold for opening the gate by applying a positive offset (up to 25 dB) relative to the closing threshold’s value. Put another way, raising the Hysteresis control makes the gate open at a higher threshold than it closes.

When setting up bx_console’s gate on a stereo track, first set the plug-in’s Stereo mode to Digital so that both channels load the same channel strip; otherwise, the gates for the two channels may not close at the same time and threshold level. Set the Threshold control higher than an acceptable noise level but low enough that it won’t prematurely cut off the desired signal’s decay. Raise the Hysteresis control (rotating the knob clockwise) until the quietest attack of desired signal—from a plucked guitar string or a tom strike, for instance—barely gets muted, and then back off the control slightly; around 10 dB of hysteresis usually does the trick on electric guitar tracks. With both controls set up properly, the gate will smoothly close at the threshold setting to attenuate noise, and it won’t reopen until the input signal exceeds the higher gate-open value determined by the Hysteresis control. No chatter!

Additional features manage the noisiest of tracks. bx_console’s EQ can be placed in the gate’s internal sidechain to filter the signal the detector hears (for example, to make the gate ignore loud hiss or rumble). Alternatively, the gate’s action can be triggered by another track routed to its external sidechain input. Release and Range controls respectively adjust how fast the gate closes and its maximum attenuation.

WAVES EMO D5 DYNAMICS

The Waves eMo D5 Dynamics plug-in wraps five dynamics processors—a gate/expander, leveler, de-esser, compressor, and limiter—into one GUI. The plug-in’s Parallel Detection technology makes each processor respond not only to the dry signal but also to its companion processors’ signals, helping to avoid excessive compression.

Fig. 2. You can prevent the gate in Waves’ eMo D5 plug-in from chattering by setting an offset for the closing threshold with respect to the opening threshold. The Close control (in the upper-left section of the GUI) adjusts the offset in decibels. eMo D5’s excellent gate provides separate Open Threshold and Close (threshold) controls (see Figure 2). The Close control provides a consistent negative offset (up to -48 dB) to the Open Threshold control as you adjust the latter. Set the Open Threshold control as high as you can without muting your desired signal. Then lower the Close control until background noise is attenuated. A Close setting of about -10 dB should gate most electric guitar tracks without chattering.

Attack, Hold, and Release controls govern how quickly eMo D5’s gate opens and closes. The Floor control adjusts the maximum attenuation allowed. Highpass and lowpass filters condition the signal for both the internal and external sidechains.

Once you’ve used a gate with separate opening and closing thresholds, you’ll never want to go back to fiddling with basic gates. It’s an open-and-shut case.